Perform a study to examine the relationship between trends in the timing of childbearing and various social, economic, and demographic factors in the U.S. during the period 1950-1977. Two measures of fertility timing will be addressed--median age at first birth and average interval between births. The socioeconomic factors to be considered are (1) shifts in medial age at marriage for men and women; (2) increasing levels of educational attainment; (3) changes in employment patterns of women; and (4) changes in the relative econoimic status of young men. Based on time series data from 1950 through 1977 the Contractor will formulate and estimate a behavioral model relating median age at first birth and the average cohort birth interval to the socioeconomic measures of age, education, employment and economic well-being mentioned above.